1. Field of the Invention
The present general inventive concept relates to a pan and tilt apparatus usable with a camera, and more particularly, to a driving mechanism to cause panning and tilting motions of a camera.
2. Description of the Related Art
A pan and tilt apparatus usable with a camera is an apparatus to rotate the camera mounted therein, about both a vertical and a horizontal axes in order to expand a filming region of the camera. The pan and tilt apparatus has two basic motions including a tilting motion (i.e., rotation in a vertical direction) and a panning motion (i.e., rotation in a horizontal direction).
As an example of a conventional camera panning and tilting apparatus, Korean Utility Registration No. 273675 discloses a pan and tilt camera comprising a signal input unit having various signal input means for complete scanning of a location of interest, a housing containing a control unit which processes input signals of the signal input unit and a pan motor which rotates upon receiving commands from the control unit, a rotating plate provided with a tilt motor and a monitoring camera using a bracket, and a horizontal rotating device coupled to the housing by means of a shaft and adapted to cause the rotating plate, in a fixed position, to undergo a horizontal rotation under operation of the pan motor.
The above described pan and tilt camera, however, experiences a problem in that the pan motor unnecessarily rotates the tilt motor, in addition to the camera, because of an excessive load applied thereto.
In an attempt to solve the problem described above, Korean Patent Publication No. 2002-63676 discloses a pan and tilt driving apparatus usable with a camera basically comprising a camera mounting structure, an independent-motion transmission unit for allowing panning and tilting motions of the camera mounting structure to be independently performed relative to each other, a panning motion performing unit usable with the camera mounting structure, a tilting motion performing unit usable with the camera mounting structure, and a fixed plate which supports both the panning motion and tilting motion performing units.
The panning motion performing unit includes panning driving means (e.g., an electric motor), a driving gear driven by the pan driving means, and a driven gear that engages and is rotated by the driving gear and is coupled to one end of a fixed frame. The tilting motion performing unit includes tilting driving means (e.g., an electric motor), a pinion rotated by the tilting driving means, and a rack that engages and is vertically moved by the pinion to vertically move the camera mounting structure.
The tilting motion in the above described pan and tilt driving apparatus is achieved at a rear end of the camera, which is hingeably coupled to the fixed frame, and rotates about a hinge axis thereof while being vertically shaken when the rack is vertically moved along the pinion rotated by the tilting driving means. With such a structure, however, since a tilting angle of the camera varies in a non-linear pattern relative to a rotating angle of the motor, an algorithm for calculating the relationship between the tilting angle of the camera and the rotating angle of the motor is needed in order to control the tilting angle of the camera to a desired value. This calculation is complex and results in difficult control operations to be performed by a control unit.